In general, a mechanical system having a rotating part and a sliding part includes an oil tank or an oil-supplying path for circulating and supplying oil to various components constituting the rotating or sliding part of the mechanical system or peripheral components thereof, and thereby smoothly operates each component while preventing them from becoming worn.
The quality control of the oil in such a mechanical system is conventionally performed by chemical analysis, but chemical analysis takes a long time after oil sampling to give a result. Therefore, quality control cannot be done in a timely manner. Accordingly, there is a demand for developing an apparatus for detecting the state of oil degradation, and some have been proposed.
For example, in the “engine-oil degradation detecting apparatus” disclosed in Japanese Unexamined Patent Application, Publication No. Hei 10-78402, a method has been proposed in which the oil pan of an engine is provided with a resistance sensor for measuring the electrical resistance of the oil, and the driver is informed of the need for an oil change when the measured electrical resistance value of the oil is decreased to a degradation resistance value that is set in advance.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. Hei 10-78402